Ti3Ni4 precipitation features in heat-treated grain / subgrain nanostructure in Ni-rich TiNi alloy

Poletika, T. M.; Girsova, S. L.; Лотков, А. И.

doi:10.1016/j.intermet.2020.106966

Cited by 21 publications

(6 citation statements)

References 33 publications

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“…This indicates that Ni 4 Ti 3 particles are formed in the matrix after long-term aging treatment, consistent with previous studies [42,50]. The nucleation of Ni 4 Ti 3 precipitates is energetically favorable in the places of B2 austenite lattice distortion, dislocations, grain boundaries, and sub-grain boundaries [3,54]. The diffraction spots at 1/3<110> B2 (marked by yellow arrow) are also identified, indicating that the aged samples are in the R-phase at room temperature [55].…”

Section: Microstructuresupporting

confidence: 88%

Superelasticity of Geometrically Graded NiTi Shape Memory Alloys

Chen,

Xi,

Jiang

et al. 2023

Metals

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A stress plateau with a strain of 5–8% normally occurs during the stress-induced martensite transformation (SIM) of NiTi shape memory alloys. Within the stress plateau, the correlation between the stress and strain is lost, which limits their application in certain fields which require accurate control of inelastic deformation. In order to address this limitation, a series of step-like NiTi samples with graded cross-sectional area were designed and fabricated. Multiple stress plateaus were achieved by varying the sample width and adjusting the number of steps; for instance, two and three stress plateaus were obtained in the samples with two and three steps, respectively. Also, linear force–strain response was obtained by changing gradually the width of the samples. The functional stability of the geometrically graded samples was significantly improved by incomplete recrystallization annealing (600 °C) followed by low-temperature (250 °C) aging treatment. The incompletely recrystallized specimens contained many dislocations and grain and sub-grain boundaries, which promoted the uniform precipitation of Ni4Ti3 nanoparticles during aging treatment. The homogeneously and densely dispersed Ni4Ti3 nanoparticles were able to strengthen the matrix considerably and prevent plastic activities during stress-induced martensite transformation. As a result, the functional stability of the geometrically graded NiTi samples was much improved. After aging at 250 °C for 120 h, all the samples showed a small residual strain of <1.0% after 20 loading–unloading cycles.

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Section: Microstructuresupporting

confidence: 88%

Superelasticity of Geometrically Graded NiTi Shape Memory Alloys

Chen,

Xi,

Jiang

et al. 2023

Metals

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“…Among the three types of initial (before aging) structures, the cold-drawn material exhibits the highest defect density (ρ ∼ = 10 12−13 cм −2 [29]), with a relatively uniform distribution. The Ti 3 4 precipitates that nucleate in this structure remain within the limit of 3−5 nm due to competing growth under similar conditions [8,26].…”

Section: Discussionmentioning

confidence: 93%

“…In the SAED image, the superposition of arc reflections from the nano-subgrains and point reflections from nano-sized grains distributed over a ring can be observed, and the reflections of the (110) B2 , (221) R , and (131) B19 are detected. It is believed that aging is suppressed at this temperature; nevertheless, the reflections (003) of Ti 3 Ni 4 precipitates are also detected; their interpretation was performed using data from [26].…”

Section: Resultsmentioning

confidence: 99%

On Structural Sensitivity of Young’s Modulus of Ni-Rich Ti-Ni Alloy

Рыклина

Murygin

Komarov

et al. 2023

Metals

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When developing bone implants, Young’s modulus is one of the primary characteristics of the material that should be considered. This study focuses on regulating the modulus of Ti-50.8 at.% Ni alloy by varying the grain/subgrain size as well as the initial structure using subsequent aging at 430 °C for 10 h. After post-deformation annealing (PDA), the temperature dependence of Young’s modulus exhibits a pronounced V-shaped character with a minimum at the onset temperature of the forward martensitic transformation, Ms, regardless of the structure. The grain/subgrain size of B2-austenite strongly affects the modulus magnitude. This effect is ambiguous for a material with a grain size range of 0.13–3 µm and depends on the test temperature. The effect of aging on the modulus reduction depends on the initial structure; it is most pronounced in an alloy with a relatively coarse grain size of 9 µm and brings a decrease of 3.8 times at a temperature of 37 °C. Aging of the initially recrystallized Ni-rich NiTi alloy makes it possible to obtain a вone-like elastic modulus of E = 12–13 GPa at an operating temperature of 37 °C. An ultrafine-grained substructure exhibits the same Young’s modulus values in the low temperature range from −100 to 25 °C.

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“…The kinetics of precipitation hardening during heating in severely deformed alloys of the Ti-Ni system changes in the same complex way [ 30 , 31 , 32 ]. Ti-Ni alloys, when exposed to HPT, amorphize.…”

Section: Introductionmentioning

confidence: 99%

Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy

et al. 2023

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The Ti-18Zr-15Nb shape memory alloys are a new material for medical implants. The regularities of phase transformations during heating of this alloy in the coarse-grained quenched state and the nanostructured state after high-pressure torsion have been studied. The specimens in quenched state (Q) and HPT state were annealed at 300–550 °C for 0.5, 3, and 12 h. The α-phase formation in Ti-18Zr-15Nb alloy occurs by C-shaped kinetics with a pronounced peak near 400–450 °C for Q state and near 350–450 °C for HPT state, and stops or slows down at higher and lower annealing temperatures. The formation of a nanostructured state in the Ti-18Zr-15Nb alloy as a result of HPT suppresses the β→ω phase transformation during low-temperature annealing (300–350 °C), but activates the β→α phase transformation. In the Q-state the α-phase during annealing at 450–500 °C is formed in the form of plates with a length of tens of microns. The α-phase formed during annealing of nanostructured specimens has the appearance of nanosized particle-grains of predominantly equiaxed shape, distributed between the nanograins of β-phase. The changes in microhardness during annealing of Q-specimens correlate with changes in phase composition during aging.

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Ti3Ni4 precipitation features in heat-treated grain / subgrain nanostructure in Ni-rich TiNi alloy

Cited by 21 publications

References 33 publications

Superelasticity of Geometrically Graded NiTi Shape Memory Alloys

Superelasticity of Geometrically Graded NiTi Shape Memory Alloys

On Structural Sensitivity of Young’s Modulus of Ni-Rich Ti-Ni Alloy

Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy

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